Flame-retardant polyesters

ABSTRACT

FIBERS AND OTHER SHAPED STRUCTURES OF POLYESTERS SUCH AS POLYETHYLENE TEREPHTHALATE ARE RENDERED FLAME-RETARDANT BY THE INCORPORATION OF POLYVINYL DIPHENYL PHOSPHINE OXIDE.

United States Patent Int. Cl. C09k 3/ 28 U.S. Cl. 260--873 1 ClaimABSTRACT OF THE DISCLOSURE Fibers and other shaped structures ofpolyesters such as polyethylene terephthalate are renderedflame-retardant by the incorporation of polyvinyl diphenyl phosphineoxide.

This is a continuation of our co-pending application, Ser. No. 54,010,filed luly 10, 1970 and now U.S. Pat. 3,681,281.

This invention relates to flame-retardant compositions. Moreparticularly, this invention relates to flame retardant polyestercompositions comprising various monomeric phosphine and diphosphineoxides and polymeric phosphine oxides.

Fibers and films made from polyesters such as polyethylene terephthalatehave found wide acceptance, but exhibit flame retardance on the order ofthat of cotton, which is somewhat less than might be desired. Atpresent, there is no additive in commercial use to impart thereto a moredesirable level of flame retardance.

It has been suggested in U.S. Pat. No. 3,370,030 that thermoplasticcompositions may be rendered flame-retardant by adding a synergisticcombination whose critical components are a chlorinated hydrocarbon andcertain diphosphine oxides. When the combination is added to thethermoplastic polymer polyethylene terephthalate, it has been discoveredthat it leads to degradation of the polymer at temperatures sufiicientto yield a melt suitable for spinning, on the order of 280-299 C. Hencethis proposed synergistic combination is not a practical solution to theproblem of flammability of polyethylene terephthalate.

It is accordingly an object of this invention to provide a materialwhich may be added to polyester fiber and film forming masses, whichadditive material imparts flame retardance.

It has been found, unexpectedly in light of the teachings of U.S. Pat.3,370,030, that tertiary phosphine oxides, in the absence of chlorinatedhydrocarbon, may be used to impart acceptable levels of flame retardanceto polyester fiber and film forming masses at low weight withoutdeleteriously aflecting other properties of the polymer and with apositive effect on some. The phosphine oxides may be monomeric, carryinghydrocarbon radicals, e.g. alkyl, aralkyl, aryl and alkenylsubstituents, optionally substituted with chlorine, bromine, or othersubstituents known to be inert or having a flame-retardant effect, suchas methyl, ethyl,-propyl, hexyl, octyl, allyl, benzyl, 3,5-

dichlorobenzyl, tolyl,-hydroxyethyl, carboxyethyl, and the like, andespecially phenyl. Alternatively, di-phosphine .oxides maybe employedwherein two phosphorus atoms arelinked byabifunctional group such aslower alkylene, e.g. ethylene, or arylene eg; phenylene, xylylene,biphenylene, and the like, with the other substituents as above.

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As noted, it is possible for the tertiary phosphine oxides to carryalkenyl substituents such as vinyl, allyl, and the like, in which casethey may be polymerized before or after extrusion. Representativephosphine oxides include tributyl phosphine oxide, triphenyl phosphineoxide, methylene bis-diphenylphosphine oxide, ethylene bis-diphenylphosphine oxide, xylylene bis-di-phenyl phosphine oxide,poly-vinyl-di-phenyl phosphine oxide, tribenzyl phosphine oxide,tris-hydroxyethyl phosphine oxide, dihydroxyethyl phenyl phosphineoxide, tris-carboxyethyl phosphine oxide, and the like.

The amount of additive included in the polymer depends on the level offlame retardance desired in a particular application of a polyesterfiber or film forming mass. About 10 weight percent or more of theadditives will impart self-extinguishing properties to the polyestermass. When the additive level is lowered to below about 5 weight percentthe polyester mass is no longer selfextinguishing but still resistsburning better than such masses without the additive. At a level ofabout 1 weight percent, while flammability is reduced, it is notsufliciently flame retardant for most purposes. Larger amounts thanthose indicated serve no purpose.

In accordance with a further aspect of the invention there may also beincorporated along with the phosphine oxide a flame retardantsynergistic additive. Representative materials includetriphenylmelamine, benzil and dibenzyl Surprisingly, it has been foundthat the effect of relatively small amounts of phosphine oxide plussynergist is far greater than the expected cumulative effect, theadditives alone having only a slight effect. To date the exact mechanismof the interaction is not known. The synergist may be employed inamounts by weight up to about 5% or more of the polyester althoughadvantageously it is present in less than about 2.5%, preferably about 1to 2%. Smaller amounts can also be used but for significant synergisticaction the indicated minimum is found desirable. When employed,preferably the synergist is present in about 10 to 30% and especially 15to 25% by weight of the phosphine oxide.

The various monomeric phosphine and diphosphine oxides and polymericphosphine oxides of this invention may be produced by any knownprocedure, such as the direct oxidation of the corresponding phosphine,the reaction of the corresponding chloro-phosphine with thecorresponding glycol,- polymerization of the corresponding vinylcompound and the like.

; The novel flame-retardant additives claimed herein may be incorporatedin the polyester by any known method. -For example, the materials may beadded by blending themwith theupolyester in powder form and thereafterforming thedesired ultimate product. Alternatively the additives maybedissolved and injected into molten poly- ,ester'and coextruded, or theadditives and polyester may :..b0..th be dissolved,.the solutionscombined and formed into shaped structuresbywet or'dry spinning. If thepolyester is first formed into a structure such as a fiber, theadditives in solution may be padded thereon and allowed to penetrate,possibly with the aid of heat to accelerate the migration. The fibrousstructure may be in the form of a fabric possibly blended with otherfibrous materials such as cotton, rayon, nylon, acetate, acrylics, andthe like. It is also within the scope of the invention to incorporateadditional ingredients such as plasticizers, dyes, pigments, heat andlight stabilizers, antioxidants, antistatic agents, photochromicmaterials and the like into the flame-retarded polyesters along with thenovel additives.

Polyesters as employed herein have reference to fiberforming polymers ofglycols and dicarboxylic acids. Representative glycols include aliphaticand especially lower alkylene glycols or polyglycols as well ascycloaliphatic or aromatic glycols, e.g. ethylene glycol, butyleneglycol, ethylene diglycol, dimethylolcyclohexane, and the like.Representative dicarboxylic acids include the aromatic and aliphaticacids, especially terephthalic, isophthalic and adipic acids althoughother acids such as bi-benzoic acid, 4,4'-dicarboxyphenyl methane,napthalene dicarboxylic acid, sebacic acid, and the like, may be presentalone or as copolymerized moieties. Of these, poly-lower alkylene glycoltcrephthalates and especially polyethylene and polybutyleneterephthalates are preferred. A small proportion of other substances maybe copolymerized therewith to modify dyeability or for other purposes,e.-g. 5-sulfoisophthalic acid.

The invention will be further described in the following illustrativeexamples wherein all parts are by weight unless otherwise specified.

EXAMPLE I (a) 95 parts of chip of polyethylene terephthalate of 0.88 IN.are dry blended with 5 parts of tri-phenyl phosphine oxide and the blendmelt spun at 290 C. into a 34 filament yarn of 143 denier having an LV.of 0.7. 0.25 gram of filament is rolled by hand into a loose ball, heldin a pair of tweezers and moved about in the yellow portion of the flameof a butane cigarette lighter. After the initially fluffy ball hadbecome consolidated, but before melting, the sample is held steady in anattempt to ignite it. Compared to a control containing notriphenylphosphine oxide which ignites and burns, the sample resistsburning.

(b) A sample similarly prepared but containing parts oftri-phenylphosphine oxide is self-extinguishing, i.e. when removed fromthe flame it will not support combustion. I

(c) Another sample containing 5% of triphenylphosphine oxide and 1% ofdibenzyl is also self-extinguishing.

(d) The same result is achieved if the dibenzyl of (c) is replaced bybenzil.

EXAMPLE II Example 1(a) is repeated, replacing the tri-phenylphosphineoxide with 10% of xylylene bis-di-phenylphosphine oxide, melting point330-333 0., prepared from di-phenyl chlorophosphine and xylylene glycolin accordance with the following equations:

The resulting fiber is self-extinguishing. Because the additive meltshigher than the polyester, it is dispersed in the fiber like an organicfiller.

EXAMPLE HI Example 1(a) is repeated, replacing the tri-phenyl phosphineoxide with 5% of ethylene bis-di-phenylphosphine oxide, melting point272-4 (3., prepared from di-phenyl chlorophosphine and ethylene glycol.The lustrous homogeneous fibers are self-extinguishing.

EXAMPLE IV (a) Replacing the phosphine oxide of Example 1(a) withtributyl phosphine oxide, vinyl di-phenyl phosphine oxide, or poly-vinyldi-phenylphosphine oxide gives substantially similar results. 7

(b) 5% of xylylene bis-di-phenylphosphine oxide gives a fiber which isflame retardant; a 7% blend is even more difiicult to ignite.

(c) 2.5% of ethylene bis-di-phenylphosphine oxide and 2.5% of polybenzylgives a fiber which is flame retardant whereas 5% of either of thesesubstances alone is less effective.

(d) 2% of ethylene bis-di-phenylphosphine oxide and 1% oftriphenylmelamine gives a fiber which is as flame retardant as onecontaining 5% of ethylene bis-di-phenyl; phosphine oxide alone.

The same combination incorporated in the same manner into a nylon fiberis without effect. Nylon fiber burns even if each of the foregoingingredients is present simultaneously to the extent of 5% by weight.

Not only are the physical properties unimpaired to a significant extentbut, in some respects, they are enhanced. Thus if hoselcgs knit from thefiber of Example 1(a) and a control containing no additive are dyed in adyebath at C. containing 1% by weight of Resoline Blue FBLD as arepresentative disperse dye, the fiber containing the additive dyes to amuch deeper shade. This is partially due to an increase dye pickup butis also partially due to a greater coloring power as evidenced by thefact that even when the dye pickups are at the same level (by dyeing thefibers separately under difierent conditions) deeper color will beapparent in the sample containing the additive. Substantially similarresults are achieved with other disperse dyes.

While the invention has particularly been described with reference tofunicular structures such as fibers and films, it is applicablegenerally to shaped structures of polyesters as defined in the FederalTrade Commission Rules promulgated pursuant to the Textile FiberIdentification Act.

The polyester fibers of the present invention are well suited for broaduse in the textile, apparel and industrial fields. In the apparel field,they may be used for a variety of mens, womens and childrens wear in aform, in blends with other fibers such as cellulosic fiber, wool and thelike. Some applications for 100% polyester, or in blends with otherfibers are in: mens and boys shirts, suits, slacks, sportswear,uniforms, and the like. Important home furnishings applications includefiller products such as pillows and comforters, sheer curtain fabric andthe like. In addition, many other applications, such as nonwovenmaterials, and the like are possible. Many equivalent modifications willbe apparent to those skilled in the art from a reading of the abovedescription with out a departure from the inventive concept.

What is claimed is:

weight polyvinyl diphenyl phosphine oxide.

3,356,631 12/1967 Jackson, Jr. et a1. 260-312 1. A flame-retardantshaped structure comprising poly 3,480,582 11/1969 Brooks 26045.75(ethylene terephthalate) and from 1 to 9 percent by 3,502,730 3/ 1970 Mon et a1 260'606-5 3,597,387 8/1971 Starr et a1 26037 5 3,668,172 6/1972Jones et a1 260-32.6 References Cited 3,674,748 7/1972 Iliopulos et a1.260-75 UNITED STATES PATENTS DONALD E. CZAJA, Primary Examiner Morris eta1 R. A. WHITE, Assistant Examiner Gillham et a1 260-887 10 Miller260-80 US. Cl. X.R. Gillham et a1 260887 26045.7 P

